docs: def zap_disk(block_device):
      '''
      Clear a block device of partition table. Relies on sgdisk, which is
      installed as pat of the 'gdisk' package in Ubuntu.
  
      :param block_device: str: Full path of block device to clean.
      '''
      # https://github.com/ceph/ceph/commit/fdd7f8d83afa25c4e09aaedd90ab93f3b64a677b
      # sometimes sgdisk exits non-zero; this is OK, dd will clean up
      call(['sgdisk', '--zap-all', '--', block_device])
      call(['sgdisk', '--clear', '--mbrtogpt', '--', block_device])
      dev_end = check_output(['blockdev', '--getsz',
                              block_device]).decode('UTF-8')
      gpt_end = int(dev_end.split()[0]) - 100
      check_call(['dd', 'if=/dev/zero', 'of=%s' % (block_device),
                  'bs=1M', 'count=1'])
      check_call(['dd', 'if=/dev/zero', 'of=%s' % (block_device),
                  'bs=512', 'count=100', 'seek=%s' % (gpt_end)])